نشریه علوم کشاورزی و منابع طبیعی
سال یازدهم شماره 2 (پیاپی 42، تابستان 1383)

The present study was fulfilled with the aim of investigating the effects of process variables on APMP (alkaline peroxide mechanical pulping) pulp brightness and yields of P.alba to produce high yield pulps suitable for making writing and printing papers. The wood samples have been prepared from the poplar plantation fields in the area of Maragheh Paper Company and converted to acceptable chips by MWPI industrial chipper. Based on the results obtained in the preliminary experiments (1), chips prostrating time of 20 minutes, impregnation times of 20 minutes for first stage and 9o and 105 minutes for second stage, total caustic soda charge of 6 and 7 % with usage rations of 40, 50 and 60% of total caustic in first impregnation stage, total hydrogen peroxide charge of 5% with usage ratio of 25% in first impregnation stage, pulp consistency of 32-34 and 23% in first and second impregnation stages, respectively, were selected and studied as effective process variables to achieve high yield APMP pulps with pulp brightness of about 80%. The results have shown that; at caustic soda charge level of 6% with usage ratio of 60% of total caustic in first impregnation stage and treatment time of 105 minutes at second impregnation stage, it would be possible to produce APMP pulp with 81.9% brightness and relatively high pulp yield of about 88%. At total caustic charge of 7% with similar usage ratio, APMP pulp of 79.9% brightness at pulp yield of 86.8% in treatment time of 90 minutes, and APMP pulp of 80.2% brightness at relatively low pulp yield of 85.3% can be produced in treatment time of 105 minutes at second impregnation stage. By reducing the treatment time at second impregnation stage and using lower usage ratio of total caustic in the first impregnation stage, APMP pulps have higher yields but at lower brightness.

Rivers under different hydro-morphological regimes, demonstrate different flow behavior as normal, debris, mud and flood flows. Spatial and temporal differentiation of these flows according to granulometric characteristics of remainder sediments is of high importance in implementation of watershed management projects especially in river flood plains. The Ziarat watershed contains debris and mud flows in summer that threat the water reserviors of the Gorgan city and touristic sites along the main stream as flash and periodically. In this study for the differentiation of flood flows, after three flow events in 26/27 July 1999, 26 August 2000, and 15/16 October 2000, 37 sediment samples have been selected randomly along the suitable reach of main stream. Then, after granulometric tests by wet sieving and hydrometry, and related curves, key granulometric indices including Trask, Symmetry, Inclusive graphic standard deviation and Krumbein index have been calculated. The sedimentology studies showed that those three flow events were high sediment flows; the first one is determined debris flow and the other two events are known as mud flow. The statistical analysis of variance resulted that, there are significant differences between first and other two flow events at 0.05 levels. The analysis of variance also showed that for particles sizes of less than 50% frequency, the difference between three flood types is not significant but for particles of higher than 50% frequency, the differences are highly significant.

Artificial drying of rough rice products is one of the most common methods of its preservation. Rapid drying can increase brittleness and induce internal cracks which predispose the product to breakage during subsequent activities. The drying process must be understood and product to breakage during subsequent activities. The drying process must be understood and controlled so that design guidelines which reduce or minimize drying damage to rough rice can be established and improved. This requires an accurate description of the drying mechanism. A finite element formulation and solution of a set of linear and nonlinear coupled conductive heat and diffusive moisture transfer equations to improve grain drying simulation of ax symmetric bodies is presented. Ax symmetric linear triangular elements with two degrees of freedom per node are used to decretive the rice grain in both models. One medium grain, "Binam", was used. During the thin layer drying, moisture was measured every minute. Good agreement has been observed when the output of nonlinear model was compared to experimental data obtained by others. Relative deviance average that calculated of linear and nonlinear model with experimental data, respectively 10.5% and 3.5%. This result shows that nonlinear is near experimental data. Nonlinear model is used for moisture simulation of rough rice drying. The simulated moisture profile and gradient are directly usable for stress cracking analyses of rough rice. The results of the finite element analysis can be used for rough rice quality evaluation and drying simulation studies.

Long-term cultivation of rice in paddy fields along with such chemical fertilizers as nitrogen and phosphorus, without using the other nutrients required for plants, and the natural limitations of soil have resulted in available phosphorus accumulation and available zinc reduction in soil. High yield Neda and Local Tarom varieties are the main strategic rice varieties, which are grown in Mazandaran province. Several reports have indicated that rice is a sensitive crop to zinc deficiency. Disorder is common in flooded fields and in such soils as sodic, calcareous, organic ones, and in soil with poor drainage conditions. In order to investigate the effects of Zinc sulphate (ZnSO4,7H2O) fertilization on the yield of two varieties (i.e. Tarom and Neda) an experiment was conducted in completely randomized block design in 11 sites of East of Mazandaran. The experiment was done on Neda variety in 8 sites and on Tarom in 3 sites. Treatments included 0, 50, 100 and 150 kg of zinc sulhate with 3 replications. Land preparation was done on the basis of the traditional methods in farming. The dimensions of plots were 3x4 meters with 165 rice plants in each plot. Eighty plants were harvested from each plot, the yield was calculated on the basis of standard moisture of 14%. Results have shown that there existed significant differences among the average yield in Neda var. treatments at 5% level. Furthermore, the yield increased to 11.6% in comparison with the control. The reason for the lack of significant difference of yield in Bushel site was the high level of soil zinc. On the contrary, the low level of soil zinc Aristech site resulted in significant differences in three treatments in comparison with the control. Considering several experiments of different varieties in several countries and considering the results of this research, Neda, which has high yield, is a sensitive variety to zinc deficiency. It is inevitable to pay attention to the real nutrition requirement of this variety. The fertilization of zinc sulphate on Tarom variety has not had a positive and economic response.

The Agaricus bisporus breeding, has always been problematic. In this mushroom, secondary homothallism causes majority of basidiospores produce the self-fertile heterokaryons, while homokaryons, which are important in the breeding, are infrequent. The main objective of this study was the utilization of variation among pure isolates and isolates generated through multi spore cultures for the Agaricus bisporus breeding. The basidiospore cultures of several commercial exotic and domestic strains were prepared. Single and multi spore cultures were isolated and subjected to spwan and fruit bodies production. Based on colony type and growth rate, variation of basidiospores in solid culture medium, spawn and in compost was examined. The relationship between classes of colony types, growth rates and the yield was examined. The results showed that isolates with low growth produced no mushroom or had a few, but in majority of isolates with high growth, a high or moderate yield was observed.

Induction and selection for salt stress tolerance in plants by synchronized application of tissue culture and mutation is a most useful approach for creation of salt stress tolerant plant. In order to study the effect salt stress tolerance of irradiated calli in soybean, an experiment was conducted in 2001 in tissue culture laboratory of NRCAM in a completely randomized design as factorial experiment. In this study we found some salt tolerant cells among cultured calli of three soybean cultivars (KW 506, B.P. and L. 17), using this approach. We selected those cells after irradiation of calli with Gamma ray and various concentration of salt in callus weight increase (w2-w1), callus weight increase ratio [(w2-w1)/w1)] and the percentage of necrotic calli percentage. Among different doses of Gamma ray, "10 Guy" was the best, and decreased necrotic calli percentage. Despite of somaclonal variation, irradiation treatments affected the creation of tolerance trait in calli, so that a few tolerant calluses obtained up to 1% of salt (NaCl).

An experiment was designed to determine the lower thermal threshold, and degree-days requirements of onion thrips, Thrips tabaci Lindeman. Developmental time of the insects, collected from cotton fields in Kashmar-Iran, was recorded at four different temperatures with 60-70% RH and a photoperiod of 16: 8 (L: D) h. The life cycle from egg to adult emergence lasted 27.1, 21.0, 15.3 and 11.3 days at 20, 23.5, 26 and 34 °C, respectively. Shortest developmental time was observed at 34 °C. Development time increased linearly with the decrease of temperature. The longest development time was observed in the larval stage about 41% of the total developmental time. Similarly, the developmental time percentages for egg, pupae and prepupae stages was 28, 18 and 13, respectively. The highest rate of development was observed in prepupae stage, was found to be the most temperature sensitive. The developmental times for egg, larvae, prepupae and pupae were 4.3, 5.6, 2.0 and 3.4 days, respectively at 26°C. Lower thermal threshold of the insect was 9.89C, and degree-days for one generation was 269.6.

To study the effect of planting arrangement on quantitative and qualitative properties of cotton (cv.Sahel) under intercropping with berseem clover (cv. Carmel), an experiment was conducted as split plot factorial in randomized complete block design in 1998 at Hashemabad station, Gorgan. The main plots were two planting arrangements of cotton (60x27 and 80x20 cm) and subplots were factorial of seed rates and planting times of berseem clover. The planting arrangement of 60x27cm resulted in highest plant hieght, number of reproductive branches, number of boll per plant, and total yield of seed cotton. Technological properties of fiber of 60x27cm were better in comparison to 80x20cm. It seems that the planting arrangement of 60x27cm is an appropriate planting arrangement for cotton. Seed rate and planting time of berssem clover and interactions of experimental factors had no effect on cotton.

To study the genetic variation and yield potential of some indigenous safflower land races, an experiment was conducted at the research farm of Isfahan University of Technology, in 1999-2000. The experiment was arranged in a randomized complete block design with four replications in which the treatments were seven safflower land races including three from Isfahan province, and the rest from Khorasan, Markazi, Hamadan, and Kordistan provinces. The results showed that there were highly significant differences among land races for days to flowering and maturity, branches per plant, plant height, head weight per plant, seeds per head, 100-seed weight, head diameter, hull and oil percent and seed yield. However, differences for heads per plant and seed yield per plant were not significant. The highest phenotypic and genotypic coefficients of variation were obtained for seed yield per plant and seed yield per plot, respectively. However, the lowest coefficients of variation were belonged to days to maturity. Within populations, the highest variation was observed for seed yield per plant and heads per plant, and the lowest one was obtained for days to maturity. Seed yield per plant followed by seeds per head had the greatest phenotypic and genotypic correlation with seed yield, but both heads per plant and seeds per head had the greatest correlation with seed yield per plant. The path analysis showed that the seeds per head had the highest, positive and direct genetic effects on seed yield. However, heads per plant and seeds per head had the most positive and direct effects on yield per plant.

To understand some physiological aspects of low temperature tolerance in wheat, in two separate glasshouse experiments the effects of low temperature on seed germination (Exp. I) and seedling physiological traits (exp.II) in three wheat genotypes were studied. A split plot design with four replications in which different temperatures (5,10 and 20 Co, exp. I, and 10, and 20 Co, exp.II) and three genotypes (Bezostaya, Boolani, and line 518, with different degrees of cold resistance) were considered as main and sub plots respectively. Decline in temperature from 20 Co (control) to 10 and 5Co resulted in a significant increase in time to 50% germination and a significant reduction in coleoptile and radicle length, dry weight and water content. At lower temperature, dry weight and length of radicle and coleoptile were greater in Bezostaya than those in Boolani and Line518. In Bezostaya seedlings, soluble sugars and chlorophyll content were higher, while leaf and crown water content were lower compared to other genotypes. Decline in temperature caused a grater increase in crown sugar content of Bezostaya compared to the two genotypes and greater increase in chlorophyll a in Bezostaya and Boolani than in Line518. These results confirmed that trait such as those measured in this study, which may guaranty a rapid emergence and establishment of seedlings at low temperature and their survival at freezing temperatures, can be considered as parts of cold tolerance mechanisms and thus may be used in breeding programs for cold climates.

The purpose of this study was to investigate the effect of salt stress on growth and symbiotic nitrogen fixation in soybean cultivars (Glycine max. L). These cultivars were planted 6 July 2001 in a randomized complete blocks design with three replicates and two factors. The factors included different cultivars (11 cultivars) and salinity levels (0,30,60,80) Mm/L. The plants were grown in sand culture and were irrigated with a Hoagland nutrient solution without nitrogen containing 0,30,60 and 80 Mm/L NaCl under greenhouse conditions. Seedlings were harvested after 60 days and leaf area, nodule number, dry wight for stem, leaf, root and nodule, nitrogen percentage and nitrogen yield were measured. Results showed that with invreasing salinity, all traits decrease. Mean comparsion showed that cultivars Dear and Gorgan3 are better then other cultivars with respect to nodule number, leaf area, dry weights, nitrogen percentage and nitrogen yield. Cultivars L.W.K and B.P were the worst. Calculation of sensitivity index showed that Dear, Hill and Gorgan3 have the highest and L.W.K and Williams have the lowest tolerance to salinity. It seems that cultivars Dear and Gorgan3 (with highest dry matter production) and Dear and Hill (with lowest sensitivity index) are promised for breeding efforts.

This experiment was conducted to investigate drsought tolerance in different soybean genotypes at germination and seedling growth stage. The plots were arranged as factorial using complete randomized blocks. The factors included different genotypes (11 genotypes of soybean) and drought stress levels (control, -3, -7 and -10 bar). Germination and growth parameters were estimated in Petri dishes and paper towels, respectively. For evaluation of drought tolerance in genotypes, sensitivity index was calculated. Results indicated when water potential reduced, germination percentage, germination rate, stem and root length, and seedling dry matter were significantly decreased. The effect of drought stress was more severe on germination rate than germination percentage. Stem length was affected by water stress more than root length. Several soybean genotypes were differently responded because of genetic difference. Interaction between genotypes and water potential for some characters was significantly positive. Genotypes of Sahar, Dari, Hagen and Gorgan-3, indicated the least drought sensitivity index. Genotypes of LBK, BP, LWK and Williams were the most sensitive genotypes.

In Guilan province olive trees are attacked by various pests among which eriophyid mites (Acari:Eriophyidae) represent an important group. An investigation was conducted during 2001-2002 for collection and identification of olive tree eriophyid mites and their natural enemies in Guilan Province. For extraction of eriophyid mites and their natural enemies DeLillo (2001) method. Was used the Amrine & Manson (1996) and Daneshvar (1980) methods, respectively were used for mounting of eriophyid mites and phytoseiid mites on microscopic slides. In this study 2 eriophyid mites, Aceria oleae (Nalepa) and Tegonotus hassani (Keifer), 4 predatory phytoseiid mites, Euseius finlandicus (Oudemans), Phytoseius Plumifer (Canestrini and Fanzago), Typhlodromus kettanehi (Dosse) and Paraseiulus soleiger (Ribaga) and 1 predatory anystid mite, Anystis baccarum L. were collected and identified. Symptoms of infestation with eriophyid mites observed in form of silvery yellow protuberances on the under side and pale green hollow on upper side of leaves. The infested leaves especially on suckers around the main trunk of olive trees became narrow and curl. Because of suitable weather conditions in Guilan Province, eriophyid mites are active during most seasons. Except Aceria oleae other species are recorded for first time on olive trees in Iran.

The performances of four empirical models of weed-crop competition were evaluated to simulate corn (Zea mays L.) yield losses caused by interference from common lambsquarters (Chenopodium album L.) in 2001 in Karaj. The experiment was conducted in a complete randomized block design with three replications. Treatments were chosen to provide five different weed densities (0, 2, 5, 10 and 15 plants m-1) and three times of weed emergence (VE, V2-V3 and V4-V5 of corn growth stage). Results showed time of weed emergence was more important than weed density, when describing the impact of common lambsquarters on corn yield. Therefore, the model based upon weed density couldnt simulate reduction in crop yield due to weed competition accurately. (R2=0.38, RMS=469.8). Although the potential and ability of this model was rejected, this model had an acceptable performance in each time of weed emergence. Parameter estimates of this model showed the relationship between weed density and crop yield loss had a tendency from rectangular hyperbola into linear, with delay in weed emergence. The model incorporating common lambsquarters density and time of emergence gave a better description of corn yield loss (R2=0.88, RMS=91.3). This model showed that common lambsquarters emergence after V8 of corn growth stage (45 DAE), couldnt reduce corn yield. Relationship between corn yield loss and common lambsquarters competition was best described by the two-parameter model of relative leaf area (R2= 0.91, RMS=0.006). The relative damage coefficient (q) of this model showed that common lambsquarters was more competitive than corn (q=1.81).

For evaluating the variation of geometry and hydraulic cross section coefficient and its simulation both in irrigation events (seasonal), and in furrow length (spatial), some experiments were developed on 24 furrows with a 60m length and 0. 75m width in a sandy-loam soil in Isfahan, in summer 2001. Furrow cross sections were measured before and after of every irrigation event using profilemeter at 5, 30 and 55 m from upstream of the furrow. Geometry and hydraulic cross section coefficient were calculated were by using of CSCM, a computer based model. Based on the results, it was seen variation both seasonal and spatial, in the furrow cross section area (A) and its dependent coefficient. Evaluation of the geometric and hydraulic coefficient variation showed no systematic trend. In addition the effect of the 1،2 coefficients were evaluated on the y-An equation. Similarly the effect of the 1، 2 evaluated on the y-Z2 equation. There was significant seasonal variation of furrow cross section area. But there wasn’t any significant variation on squared shape factor (Z2) as a hydrawlically index. A linear equation was developed for the seasonal variation of both A and Z2. Based on the results, no systematic trend was observed between spatial variations of the parameters in a furrow because of complexity.

During the recent years potato has been considered as a dominant crop in Bojnord. Importance of yield enhancement and proper utilization of inputs in potato production, necessiats policy making based on production efficiencies which was the aim of this research. Data was collected from 45 potato producers in 1998 growing season using simple random sampling method and technical efficiency was determined based on frontier production function and corrected least square method. Results showed that mean technical efficiency of potato producers was 65.6% and around 25% of farmers were using animal manure higher than optimal level. Technical efficiency was directly correlated with cultivated area but inverse relationship was obtained between technical efficiency and educational level of potato producers.

Predatory bug. A. spinidens is one of the natural enemies of lepidopteran larvae pests in Northern rice fields of Iran. The effect of feeding on the rice plant in the development and survival of nymphs, longevity and oviposition of females, and predation of A.spinidens fed with the Rice Semilooper, Naranga aenescens Moor (Lep.: Noctuidae) was studied under laboratory conditions [temperature of 25±2°C, relative humidity of 75±5% and a photoperiod of 16:8 hours (light:dark)] with the aim of improving the mass rearing of the predator. Larvae of N. aenescens were sufficiantly provided for both the treatments (with and without rice plant). Duration of the embryonic, nymphal and one generation of A. spinidens were similar in two treatments, but daily predation in each of them was significantly different, so that A.spinidens in the nymphal period preyed on 21.60±2.94 and 17.20±1.95 larvae in the presence and absence of plant, respectively. A. spindens during nymphal and adult stages fed on prey and rice plants, had improved ovipsition period, higher number of eggs and survival than those fed only on prey. Therefore, it seems that to rear A. spinidens with prey together with host plant (or sowing them in the culture containers), improves the mass rearing method of this predator.

Atriplex canescens is a shrub plant and exotic in Iran that is used for rehabilitation of destroyed ranges for a decads. Keeping in mind, the ecological reaction in ecosystem a necessity for this kind of study was felt, especially for exotic species that less information about them are available. This research accomplished in one of the pastures of eastern part of Brigand area. Sampling was done using three treatments with some repetition taken from under story of this plant, between plants and a control area. The soil chemical analyses and statistical analysis showed that factors like EC, humus% and Ca+2, Na+, K+ ions of under story treatment was significantly different that the other two treatment. The observations clearly showed that this resulted changes in under story soil condition from normal to salin and sodic.